from __future__ import annotations

from sain import Ok, Err
from sain import Some
from sain import Vec

import typing
from dataclasses import dataclass, field

if typing.TYPE_CHECKING:
    # These are just type aliases that have no cost at runtime.
    # __annotations__ needs to be imported.
    from sain import Result, Option


@dataclass
class Chunk:
    tag: str
    data: Option[bytes] = Some(None)


@dataclass
class BlobStore:
    buffer: Vec[Chunk] = field(default_factory=Vec)
    size: int = 1024

    def put(self, tag: str) -> Result[Chunk, str]:
        if self.buffer.len() >= self.size:
            # The return type of the error doesn't have to be a str.
            # its much better to have it an opaque type such as enums
            # or any data type with more context.
            return Err("Reached maximum capacity sry :3")

        chunk = Chunk(tag, Some(f"chunk.{tag}".encode("utf-8")))
        self.buffer.push(chunk)
        return Ok(chunk)

    def next_chunk(self, filtered: str = "") -> Option[Chunk]:
        # this code makes you feel right at home.
        return self
            .buffer
            .iter()
            .take_while(lambda chunk: filtered in chunk.tag)
            .next()


storage = BlobStore()
match storage.put("first"):
    case Ok(chunk):
        print(storage.next_chunk())
    case Err(why):
        print(why)